Method of compression of refuse

ABSTRACT

A PROCESS OF COMPRESSING DOMESTIC REFUSE THAT IS MADE UP PREDOMINANTLY OF PAPER WHEREIN THE TOTAL REFUSE IS COMPRESSED AT A PRESSURE BELOW ITS THIZOTROPIC POINT AND ABOVE A POINT THAT THE &#34;SPRING-BACK&#34; OF THE REFUSE BECOMES APPROXIMATELY CONSTANT.

20, 1971 L. SKENDROVIC ETAL 3,605,606

METHOD OF COMPRESSION OF REFUSE 4 Sheets-Sheet 1 Filed Oct. 23. 1968 INVENI'OR LAWRENCE SKENDROVIC VICTOR F KOONTZ Sept. 20, 1971 L. SKENDROVIC ETAL 3,605,606

METHOD OF COMPRESSION OF REFUSE Filed Oct. 23, 1968 4 Sheets-Sheet 2 DRY SAMPLE STABLE BULK DENSITY AFTER PRESSURE l5 RELIEVED BULK DENSITY 0 UNDER PRESSURE 10 2o 4o 10 so no BULK DENSITY LBS./FT.

, INVENTOR FIG. 2 LAWRENCE smvmovrc VICTOR F". KOONTZ ATTORNEY Sept. 20, 1-97! L. SKENDROVlC ETAL 3,605,606

METHOD OF COMPRESSION OF REFUSE Filed Oct. 23, 1968 4 Sheets-Sheet 3 MoisIure sam o/es l 60 Q I.

l I I I 50 m 3 I a} I I 6 I I Process 0. I L im/fafion 4o I Po/m I #5 I I I I I 30 O I I I, I l I L Mo/sfure Confenf 0 I 107, REMAINING Bulk Dens/fy I a 200);

[O l0 7. mois/ure 257- moisfure I007- moisfure Z007- moisfure l l I o 1 1 a n "I I0 20 5o so I00 no BULK DENSITY lbs/m ANDZ MOISTURE com'nzwr REMAINING MENTOR FIG. 3 LAWRENCE SKENDROVIC VICTOR F. KOONTZ BY m M ATTORNEY p 20111971 L. SKENDROVIC ETAL 3,605,606

METHOD OF COMPRESSION OF REFUSE Filed Oct. 23. 1968 w 4 Sheets-Sheet 4 Thixofrop/c Pain? of Shredded 8o n \\i\ Paper or Re'Fuse Unsafe O oerafmy Area m i v n. i A

. Thixofropic Curve H 0 Safe R mamme c opemfiny Curve Area l l l G o 9 l l l I I l I I I I I 20 I00 I60 I60 200 Z Moisfure Confenl' j- 4 mvmon LAWRENCE SKENDROVIC VICTOR F. KOONTZ ATTORNEY United States Patent Offlce 3,605,606 Patented Sept. 20, 1971 3,605,606 METHOD OF COMPRESSION OF REFUSE Lawrence Skendrovic, West Mifllin, and Victor F. Koontz,

Fairview, Pa., assignors to Eriez Manufacturing Company, Erie, Pa.

Filed Oct. 23, 1968, Ser. No. 769,944 Int. Cl. B30b 13/00 US. Cl. 100-35 1 Claim ABSTRACT OF THE DISCLOSURE A process of compressing domestic refuse that is made up predominantly of paper wherein the total refuse is compressed at a pressure below its thixotropic point and above a point that the spring-back of the refuse becomes approximately constant.

STATEMENT OF INVENTION This invention relates to treating paper and, more particularly, to a process of compressing domestic refuse.

OBJECTS OF THE INVENTION It is an object of the invention to provide an improved process of compressing paper.

Another object of the invention is to provide a process of compressing domestic refuse which is predominantly paper.

Another object of the invention is to provide a process of compressing domestic refuse which will result in an optimum bulk density.

Another object of the invention is to provide a process of compressing refuse that Will result in the optimum water removal from the refuse.

Another object of the invention is to provide a process of compressing refuse that will result in substantially a minimum spring-back characteristic.

Another object of the invention is to provide dewatering of materials other than refuse.

With the above and other objects in view, the invention comprises the processes set forth in the specification, drawings, and recited in the appended claim. The invention will be better understood from a reference to the drawings and detailed specification wherein:

FIG. 1 is an exploded view of the die used in the tests disclosed herein;

FIG. 2 is a graph showing the bulk densities of paper and refuse material compressed by various pressures and illustrating the spring-back at these pressures;

FIG. 3 is a graph showing the bulk densities and moisture contents of paper materials compressed at various pressures; and

FIG. 4 is a graph showing the thixotropic pressures of paper materials having various moisture contents.

DETAILED DESCRIPTION The tests which resulted in the present invention were carried out with the following objectives:

(1) To correlate high pressures applied to refuse relative to resulting high bulk densities, both stable and restrained.

(2) To accumulate data on the phenomena involved in water removal by compression from municipal refuse made up predominantly of paper.

As used herein, the words stable bulk density mean the bulk density when all external forces are removed from the material.

The conclusions reached as a result of the tests were as follows:

( 1) Subjection of refuse, averaging 25% moisture content, to applied pressures of 45,000 p.s.i. yields stable bulk densities of 70 lbs. per cubic foot. This value will vary predictably as a function of moisture content.

(2a) Dewatering from moisture contents as high as 200% down to moisture contents of 35% is reliably accomplished using applied pressures of up to 80,000 p.s.i. It is probably not practical to remove additional moisture below the 35 level by compression alone.

(2b) Under certain conditions of moisture content and applied pressure, refuse exhibits thixotropic characteristics; i.e., deformation under pressure reduces consistency of refuse having certain moisture content which results in fluidity rendering further compaction increasingly difficult.

THE TEST RESULTS Bulk densities A cylinder with a plunger, such as shown in FIG. 1, was used for compressing the refuse. A hydraulic press, manufactured by the K. R. Wilson Company, with a rated capacity of tons was used to supply the pressure.

The test samples consisted of confetti made from newspaper with measured amounts of Water added, as well as commercially shredded refuse. Four samples were used:

(1) a dry sample having only a natural moisture content of about 10%,

(2) a 25% moisture content sample,

(3) a 100% moisture content sample, and

(4) a 200% moisture content sample.

In FIG. 2, curve A is a graph showing the bulk density versus pressure measured under pressure and curve B shows the bulk density after the pressure had been applied and relieved. A maximum bulk density of 110 pounds per cubic foot was attained with an applied pressure of 80,000 pounds per square inch. After this pressure was relieved, the sample experienced spring-back, and the bulk density measured pounds per cubic foot.

Bulk densities of 60 pounds per cubic foot were ob tained with both samples of and 200% moisture content. This was measured after 25,000 p.s.i. had been applied and relieved (refer to FIG. 3).

A bulk density of 80 pounds per cubic foot was obtained in these tests with 5,000 p.s.i. but this was considerably less after the pressure was removed.

FIG. 3 is a plot of bulk density versus compaction pressure for refuse samples containing natural moisture, about 10%. This graph also shows moisture content of 25%, 100% and 200%.

Moisture content No moisture removal was observed from the dry sample which actually had about a 10% natural moisture content. The samples containing 100% and 200% moisture contents experienced a fairly rapid loss of moisture up to an applied pressure of 10,000 p.s.i. at which point the moisture content was less than 60% (see FIG. 3). Increases in pressure beyond this point reduced the moisture content at a much slower rate. The samples had moisture contents of about 35% after 80,000 p.s.i. had been applied. This reading of 80,000 p.s.i. may be influenced by apparent thixotropy of the material under these conditions.

According to Chemical Engineering Handbook by John H. Perry, a substance is thixotropic when deformation reduces its consistency. The lower its consistency, the more fluid-like the substance becomes. To investigate this phenomenon a number of samples of different moisture contents were prepared. Each sample was pressurized to the point where paper was observed flowing in /8 inch diameter holes drilled in the side of the test cylinder. FIG. 4 is a plot of moisture content versus applied pressure at the point of thixotropy. Also included is the K p.s.i. versus moisture content of the dry sample in order to establish a safe operating point below which little or no moisture would be removed. This is designated as the Process Limitation Point.

SUMMARY As illustrated in FIGS. 2 and 3, the bulk density of paper increases at a linear fashion at pressures above 20,000 p.s.i. Furthermore, the spring-back is substantially constant at pressures above 20,000 p.s.i., as indicated in FIG. 2. At 12,000 p.s.i., the stable bulk density of refuse is approximately equal to the density of Water.

FIG. 4 indicates that the pressure at the thixotropic point of paper tends to be constant at pressures below 20,000 psi. for paper containing moisture content above 200%.

The foregoing has lead to the discovery that when paper is compressed to a pressure just below its thixotropic point, the paper will not only obtain very nearly its maximum bulk density, but very nearly the maximum amount of water will be removed from it. Since municipal refuse is generally approximately 80% paper, it follows that municipal refuse compressed to a pressure below its thixotropic point irrespective of moisture content will result in compacted bodies of substantially the optimum bulk density.

The foregoing specification sets forth the invention in its preferred practical forms but the process disclosed is capable of modification within a range of equivalents without departing from the invention which is to be under- 5 stood is broadly novel as is commensurate with the appended claim.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process of compressing material made up predominantly of paper into the form of compacts comprising exerting a pressure approximately equal to that value which causes the material to become thixotropic,

said pressure being in excess of 20,000 pounds per square inch whereby said material reaches a stable bulk density and substantially no springback of said material results.

References Cited UNITED STATES PATENTS 3,330,088 7/1967 Dunlea 53--24 3,43 8,320 4/ 1 9,69 Raab l0043X 3,451,185 6/ 1969 Tezuka 53-22 OTHER REFERENCES Scientific American, November 1959, vol. 204, No. 5 (pages 61-67).

BILLY J. WILHITE, Primary Examiner 

